<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/54205>54205</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            clang cannot find headfiles in default search path with shared library on Windows
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          Rt39
      </td>
    </tr>
</table>

<pre>
    The source code I got was from github realease 13.0.1.

I'm trying to build clang to have the default target triple to `x86_64-pc-windows-gnu` on Windows 10(21H1, 19043.1526), so I tried to compile it with my mingw-w64(TDM-GCC 10.3.0) with the following configuration:
```
cmake -S llvm -B build -G Ninja -DCMAKE_C_COMPILER:STRING=gcc -DCMAKE_CXX_COMPILER:STRING=g++ -DCMAKE_BUILD_TYPE:STRING=Release -DCMAKE_INSTALL_PREFIX:PATH=C:/llvm -DLLVM_ENABLE_PROJECTS:STRING="clang" -DLLVM_DEFAULT_TARGET_TRIPLE:STRING="x86_64-pc-windows-gnu" -DLLVM_TARGETS_TO_BUILD:STRING="X86"
```

It worked pretty well. However, I found the size of the tool chain is unbearable large, up to about 6 GB. And I also found that through the help page [](https://llvm.org/docs/CMake.html#llvm-related-variables) which says that it can be built to use shared library by using MinGW with the parameter BUILD_SHARED_LIBS:BOOL, I followed through with the configuration:
```
cmake -S llvm -B build -G Ninja -DCMAKE_C_COMPILER:STRING=gcc -DCMAKE_CXX_COMPILER:STRING=g++ -DCMAKE_BUILD_TYPE:STRING=Release -DCMAKE_INSTALL_PREFIX:PATH=C:/llvm_mingw_shared -DLLVM_ENABLE_PROJECTS:STRING="clang" -DLLVM_DEFAULT_TARGET_TRIPLE:STRING="x86_64-pc-windows-gnu" -DLLVM_TARGETS_TO_BUILD:STRING="X86" -DBUILD_SHARED_LIBS:BOOL="ON"
```

The compiling was smooth enough, but the compiled clang cannot pass through a simple file, like say:
```cpp
//////////// source2.cpp //////////
#include<windows.h>
int main(){}
```

and the output of clang is like:
```
PS D:\cs\c++\test> C:\llvm_mingw_shared\bin\clang source2.cpp -v
clang version 13.0.1
Target: x86_64-pc-windows-gnu
Thread model: posix
InstalledDir: C:\llvm_mingw_shared\bin
 "C:\\llvm_mingw_shared\\bin\\clang.exe" -cc1 -triple x86_64-pc-windows-gnu -emit-obj -mrelax-all --mrelax-relocations -disable-free -disable-llvm-verifier -discard-value-names -main-file-name source2.cpp -mrelocation-model pic -pic-level 2 -mframe-pointer=none -fmath-errno -fno-rounding-math -mconstructor-aliases -mms-bitfields -munwind-tables -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -v "-fcoverage-compilation-dir=D:\\cs\\c++\\test" -resource-dir "C:\\llvm_mingw_shared\\lib\\clang\\13.0.1" -internal-isystem "C:\\TDM-GCC-64\\x86_64-w64-mingw32\\include\\c++" -internal-isystem "C:\\TDM-GCC-64\\x86_64-w64-mingw32\\include\\c++\\x86_64-w64-mingw32" -internal-isystem "C:\\TDM-GCC-64\\x86_64-w64-mingw32\\include\\c++\\backward" -internal-isystem "C:\\TDM-GCC-64\\x86_64-w64-mingw32\\include\\c++\\10.3.0" -internal-isystem "C:\\TDM-GCC-64\\x86_64-w64-mingw32\\include\\c++\\10.3.0\\x86_64-w64-mingw32" -internal-isystem "C:\\TDM-GCC-64\\x86_64-w64-mingw32\\include\\c++\\10.3.0\\backward" -internal-isystem "C:\\TDM-GCC-64\\include\\c++\\10.3.0" -internal-isystem "C:\\TDM-GCC-64\\include\\c++\\10.3.0\\x86_64-w64-mingw32" -internal-isystem "C:\\TDM-GCC-64\\include\\c++\\10.3.0\\backward" -internal-isystem "C:\\TDM-GCC-64\\lib\\gcc\\x86_64-w64-mingw32\\10.3.0\\include\\c++" -internal-isystem "C:\\TDM-GCC-64\\lib\\gcc\\x86_64-w64-mingw32\\10.3.0\\include\\c++\\x86_64-w64-mingw32" -internal-isystem "C:\\TDM-GCC-64\\lib\\gcc\\x86_64-w64-mingw32\\10.3.0\\include\\c++\\backward" -internal-isystem "C:\\llvm_mingw_shared\\lib\\clang\\13.0.1\\include" -internal-isystem "C:\\TDM-GCC-64\\x86_64-w64-mingw32/sys-root/mingw/include" -internal-isystem "C:\\TDM-GCC-64\\x86_64-w64-mingw32\\include" -internal-isystem "C:\\TDM-GCC-64\\include" -fdeprecated-macro "-fdebug-compilation-dir=D:\\cs\\c++\\test" -ferror-limit 19 -fmessage-length=105 -fno-use-cxa-atexit -fgnuc-version=4.2.1 -fcxx-exceptions -fexceptions -exception-model=seh -fcolor-diagnostics -faddrsig -o "C:\\Users\\sunra\\AppData\\Local\\Temp\\source2-f0124a.o" -x c++ source2.cpp
clang -cc1 version 13.0.1 based upon LLVM 13.0.1 default target x86_64-pc-windows-gnu
ignoring nonexistent directory "C:\TDM-GCC-64\x86_64-w64-mingw32\include\c++"
ignoring nonexistent directory "C:\TDM-GCC-64\x86_64-w64-mingw32\include\c++\x86_64-w64-mingw32"
ignoring nonexistent directory "C:\TDM-GCC-64\x86_64-w64-mingw32\include\c++\backward"
ignoring nonexistent directory "C:\TDM-GCC-64\x86_64-w64-mingw32\include\c++\10.3.0"
ignoring nonexistent directory "C:\TDM-GCC-64\x86_64-w64-mingw32\include\c++\10.3.0\x86_64-w64-mingw32"  
ignoring nonexistent directory "C:\TDM-GCC-64\x86_64-w64-mingw32\include\c++\10.3.0\backward"
ignoring nonexistent directory "C:\TDM-GCC-64\include\c++\10.3.0"
ignoring nonexistent directory "C:\TDM-GCC-64\include\c++\10.3.0\x86_64-w64-mingw32"
ignoring nonexistent directory "C:\TDM-GCC-64\include\c++\10.3.0\backward"
ignoring nonexistent directory "C:\TDM-GCC-64\x86_64-w64-mingw32/sys-root/mingw/include"
#include "..." search starts here:
#include <...> search starts here:
 C:\TDM-GCC-64\lib\gcc\x86_64-w64-mingw32\10.3.0\include\c++
 C:\TDM-GCC-64\lib\gcc\x86_64-w64-mingw32\10.3.0\include\c++\x86_64-w64-mingw32
 C:\TDM-GCC-64\lib\gcc\x86_64-w64-mingw32\10.3.0\include\c++\backward
 C:\llvm_mingw_shared\lib\clang\13.0.1\include
 C:\TDM-GCC-64\x86_64-w64-mingw32\include
 C:\TDM-GCC-64\include
End of search list.
source2.cpp:1:9: fatal error: cannot open file
      'C:\TDM-GCC-64\lib\gcc\x86_64-w64-mingw32\10.3.0\include\c++\windows.h': No such file or directory
#include<windows.h>
        ^
1 error generated.
```

It seems that clang only search for the first path shown on the path list. I truly have `windows.h` in ` C:\TDM-GCC-64\x86_64-w64-mingw32\include`. Also, compiling a file including `<iostream>` will be like this:
```
PS D:\cs\c++\test> C:\llvm_mingw_shared\bin\clang source2.cpp -v
clang version 13.0.1
Target: x86_64-pc-windows-gnu
Thread model: posix
InstalledDir: C:\llvm_mingw_shared\bin
 "C:\\llvm_mingw_shared\\bin\\clang.exe" -cc1 -triple x86_64-pc-windows-gnu -emit-obj -mrelax-all --mrelax-relocations -disable-free -disable-llvm-verifier -discard-value-names -main-file-name source2.cpp -mrelocation-model pic -pic-level 2 -mframe-pointer=none -fmath-errno -fno-rounding-math -mconstructor-aliases -mms-bitfields -munwind-tables -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -v "-fcoverage-compilation-dir=D:\\cs\\c++\\test" -resource-dir "C:\\llvm_mingw_shared\\lib\\clang\\13.0.1" -internal-isystem "C:\\TDM-GCC-64\\x86_64-w64-mingw32\\include\\c++" -internal-isystem "C:\\TDM-GCC-64\\x86_64-w64-mingw32\\include\\c++\\x86_64-w64-mingw32" -internal-isystem "C:\\TDM-GCC-64\\x86_64-w64-mingw32\\include\\c++\\backward" -internal-isystem "C:\\TDM-GCC-64\\x86_64-w64-mingw32\\include\\c++\\10.3.0" -internal-isystem "C:\\TDM-GCC-64\\x86_64-w64-mingw32\\include\\c++\\10.3.0\\x86_64-w64-mingw32" -internal-isystem "C:\\TDM-GCC-64\\x86_64-w64-mingw32\\include\\c++\\10.3.0\\backward" -internal-isystem "C:\\TDM-GCC-64\\include\\c++\\10.3.0" -internal-isystem "C:\\TDM-GCC-64\\include\\c++\\10.3.0\\x86_64-w64-mingw32" -internal-isystem "C:\\TDM-GCC-64\\include\\c++\\10.3.0\\backward" -internal-isystem "C:\\TDM-GCC-64\\lib\\gcc\\x86_64-w64-mingw32\\10.3.0\\include\\c++" -internal-isystem "C:\\TDM-GCC-64\\lib\\gcc\\x86_64-w64-mingw32\\10.3.0\\include\\c++\\x86_64-w64-mingw32" -internal-isystem "C:\\TDM-GCC-64\\lib\\gcc\\x86_64-w64-mingw32\\10.3.0\\include\\c++\\backward" -internal-isystem "C:\\llvm_mingw_shared\\lib\\clang\\13.0.1\\include" -internal-isystem "C:\\TDM-GCC-64\\x86_64-w64-mingw32/sys-root/mingw/include" -internal-isystem "C:\\TDM-GCC-64\\x86_64-w64-mingw32\\include" -internal-isystem "C:\\TDM-GCC-64\\include" -fdeprecated-macro "-fdebug-compilation-dir=D:\\cs\\c++\\test" -ferror-limit 19 -fmessage-length=105 -fno-use-cxa-atexit -fgnuc-version=4.2.1 -fcxx-exceptions -fexceptions -exception-model=seh -fcolor-diagnostics -faddrsig -o "C:\\Users\\sunra\\AppData\\Local\\Temp\\source2-4f4eb4.o" -x c++ source2.cpp
clang -cc1 version 13.0.1 based upon LLVM 13.0.1 default target x86_64-pc-windows-gnu
ignoring nonexistent directory "C:\TDM-GCC-64\x86_64-w64-mingw32\include\c++"
ignoring nonexistent directory "C:\TDM-GCC-64\x86_64-w64-mingw32\include\c++\x86_64-w64-mingw32"
ignoring nonexistent directory "C:\TDM-GCC-64\x86_64-w64-mingw32\include\c++\backward"
ignoring nonexistent directory "C:\TDM-GCC-64\x86_64-w64-mingw32\include\c++\10.3.0"
ignoring nonexistent directory "C:\TDM-GCC-64\x86_64-w64-mingw32\include\c++\10.3.0\x86_64-w64-mingw32"  
ignoring nonexistent directory "C:\TDM-GCC-64\x86_64-w64-mingw32\include\c++\10.3.0\backward"
ignoring nonexistent directory "C:\TDM-GCC-64\include\c++\10.3.0"
ignoring nonexistent directory "C:\TDM-GCC-64\include\c++\10.3.0\x86_64-w64-mingw32"
ignoring nonexistent directory "C:\TDM-GCC-64\include\c++\10.3.0\backward"
ignoring nonexistent directory "C:\TDM-GCC-64\x86_64-w64-mingw32/sys-root/mingw/include"
#include "..." search starts here:
#include <...> search starts here:
 C:\TDM-GCC-64\lib\gcc\x86_64-w64-mingw32\10.3.0\include\c++
 C:\TDM-GCC-64\lib\gcc\x86_64-w64-mingw32\10.3.0\include\c++\x86_64-w64-mingw32
 C:\TDM-GCC-64\lib\gcc\x86_64-w64-mingw32\10.3.0\include\c++\backward
 C:\llvm_mingw_shared\lib\clang\13.0.1\include
 C:\TDM-GCC-64\x86_64-w64-mingw32\include
 C:\TDM-GCC-64\include
End of search list.
In file included from source2.cpp:1:
C:\TDM-GCC-64\lib\gcc\x86_64-w64-mingw32\10.3.0\include\c++\iostream:38:10: fatal error: cannot open file      'C:\TDM-GCC-64\lib\gcc\x86_64-w64-mingw32\10.3.0\include\c++\bits/c++config.h': No such file or    
      directory
#include <bits/c++config.h>
         ^
1 error generated.
```

Which, the `bits/c++config.h` is actually in `C:\TDM-GCC-64\lib\gcc\x86_64-w64-mingw32\10.3.0\include\c++\x86_64-w64-mingw32\bits`.

I don't know whether there's anything to do with building shared libraries. I have tried to compile the source code switching different compilers (from gcc, TDM-GCC 10.3.0, which is based on mingw-w64 to cl, Microsoft (R) C/C++ Optimizing Compiler Version 19.30.30709 for x64) and default target triple (from x86_64-pc-windows-gnu to x86_64-pc-windows-msvc) and whether to build the shared library (which msvc cannot do so), and I finally realized that it may be the reason that I turned on the last option.

(By the way, I also tried to compile llvm with clang(getting from the realease binary), and hard as I tried, it could not pass. The linker, both ld and lld.link, complains about undefined symble when linking LLVMSupport)
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJztW1132jwS_jXkRsc-YAOBi1wQICm75OMk6dvuVY5sy6BWtnwsOUB__c5IMh8JpO3bJLtnl54UsDyaGc2MRuPHUiST1dnDnBElqzJmJJYJIxMyk5osqCJpKTMy43peRaRkVDCqGGmFftNv-Y3mqNEc2M9JIzjNiC5XPJ8RLUlUcZGQWFB7OadPjGiQkrCUVkITTcsZg6-SF4IhRaPbXPa6j922V8TegueJXChvllfQTmROvtgW0mo2gl7Q-tRqBEPS6jfbod_qBN1G0McGJUF14MkSZBnLrODAncNQYAQkW5EM1Ft4i24buDyMrrzLIXBp-jAe4GCpUMtUCiEXOJRY5imfVSXVXOaN0I0WlHJ_5jLO6HdGvHsixFNGvHM3eu-SXPP8GyXeaHg1-Of4cfg4vLm6nUzHd8Dp_uFucn3ZCEezON5QfP26n6YRnMPfmu7882Q6enz41-14m-qOWf_UVJPr-4fBdPp4eze-mHwFytvBwyegG-JAggur7Wg6_evqcXw9OJ-OgfLmH-Phw_0210YQGD_Cd009Gl8MPk8fHh8Gd5dj-Lqb3E7Hz_rs9-aGh-17__hwY0fzrPvXHjg12GtuF3HgVVl-B1cXJdN6RRZMCJ98kgv2xEqMhgn4scoT41HFfzAiU_NbSylIPKc8J1yRKo8YLWkEgSIwKLFnVWD80EhWmnTJ5blPBsBnQqiACKuZUgjfeSmrmY2ZORMFKeiMkUbnvNGBMfTmWhfK2tqZ25cl2PEikbGCr-EVxI0_15loBCHe9komqGaJ90RLjiopE5ZzHs-JoitlpUI8xzQnETNxplHVCryu5rQEawgelbRckWgFrRjCVzy__LKJ7QIGmzHNSmKD6P7T4G48epxOztHr5zc309p2OAdwJrlBrjn8r8-JR5MlHp09_7snCBAfdKMhu7l-fRo9GIdiosRYwZSvMinB0yxHr2MsRJV2fjf5tE7rEIM5rBIFVWodIxQmWoYZPQVC7Cs4RAGE7sswiYvCtZjZ8fqfW50CH3qRn1A7piHPY1ElrBEOnX39eSMc29s81ySDBACTFJeO0_PG6egVI1GXRSAfFGAMyCPWBJA-cICH5sDtPUGvNTpDmO7wYQMWfmmmNOhChvbui6CDtgiUgy5GzPbgvSc3v8wdyHQKJqFbkZ1HzdIKnMn-CHNuh9U8IRms9gJJC6n40iXWXGkqwM8jXuKtnyhp-oBPAkd3gHQ9pHpUPlsyE8Bx3CKeKwT2akw8lnHtyegb8TLMkEsP9CNefQGfMjbJSBEv4QoTp5eWjG2uTHIFY_GUQ-LD5piWmGZFxbwc8iH0xHjwMG5Nw67Rs40Mz9iMFBwyFHx4ApYbQWAcWYqJ1SskBBcsQOEolzmokGZUzz1WlrmEi1x6Ja4fYBwPb0A3SKdKl1WsZQnj4pCsUJlMeRHXoK5I8LLK0SCeNosCmMv42IuLCk3mddvQVOXMNMxYDgMF7RIWVbMZK_EWyMOUmUQQQOgsL40l2AOWK89Oazu2BF0-Gq09aeJ2J3Tr6EXPlcwaCbv9UgTA2rQVAfanC13kZwyXU-FxtVKaZbs8Xb0Gg7XXLlagmPOMpDCw7fW831H8ndkf6vERYiMaf19ANH-IsLpY_jhR_0nTbqvwB2Z-B3N-oNne3TzrrABV3-ue2hb4RtP8DYW_ncnfWqnfcM7vZ-4d2W8yK4ML6AjrpIRl5sI0wvebSvhDnbd7pgmDB9DYPLZlNC6lXV7N4vsHa2sKFQMUBIJD6UNafawjmFK4XguWzzSUsqNWs2MrCnj68-Il9UCHJVB7KRRNsedqQyBs-4EPNVYaL5ceW8ascLVSun2x_u25onCk2Bw7SQF6JJzOcqk0j7EfTRLgPSOe3LXTZwUy7U9V5SW1PwdFMaLaXUyhjBLOqiwrHLGttby02Qra1JfGAkviLLNdim0Xv6Zy3K2ASQTlUwLP79CCD1F18zPY6ZXCmMMwS3wUwuptySEW4FEBXMewPlttDXcnJvaG2GY-btLTBwg5kIM-RPJWovkQeev18yOlHUry5GOVeCNbv5tZf9-C7ybt_cLyJ0vVczACOfu-j9GiGC0R1oOUpBWZs3ILRtiiD4dIH45foyf7lLUrti0g9gbX2jovTfc-XPf2eC9Ra5fvCNhX3Vg5dV2zLmpqpocVfHXKHu62QzHOE4STnHMFRKJ7rbK95oWDFvzvIxiTwkIqiKkN8NJhcLJguYXcrFjzrxGcvr1ZN1BacIoKXEuiKtAchRNZbubQL8FwxP1rdFxDyw7NYhhYUvl7gbX1GwDFWOZQcVsTyFysamumwMi8zeGlQpxSw-yZy0WO75MsEq6dyc1bowp6mvdUIGajardJeI5Nvx8C3aZPBkJJxEE3ECu1trJE2ICjCocciquS0QxtA8IWXAhE-A1-qudcHTHGI8Z4xBiPGOMRYzxijEeM8YgxHjHGI8Z4xBj_BsbYTtssah8xxiPGeMQYjxjjEWM8Yoz_txjjJN_GomBNM7u9XyKPlvrt7bfBvAZhD2U1fwHifEdwM-Iat-W6BrvN9SDSSepcbBU6CHzi9DrA-DkM-jdx0C-4PxhBRgQ14d4BaYhkKkJjXVEhVg7V_JD55yzbbe4eGSAJVI7BqSbfc7kgizkD_Q1iC2knOAVV85Weu_MEibT7j80uYmzb2e3MmUIM154yeL79Xz873KCAUWz4JjyFEhjTsqMtFQRWz555gOGDSZ8fEhi63dhgSVsGQhG4PlRgpAokuuJQpCuZauR3h5u4h7jf29WaN1ADZ_wHqjB0gslfdY3Z90OQ1Txt9g2AvcSzCn2CO1D3n52oFd4Pa4JGL29k6imuma7NXp_ZMOba3UoOIuyosWM9IcEjCG2bcxfU7I5PeW4iC8-J8B8sWe9Wz-gKsWzkDPeUgd_hzoToqsytDfGeoArnOT4f7AQKiD9fGYoFXdnN6WYj_gtPm63mJkzcfuwe2EmjmY2FnHy7HzwCZWGybvSHISeEqvoACTbjRntZgU3qfc4-we3Sguff7QmDCDdKw33sL0Ti450a7ReUwyOPPUNQ5eA7jkNVqwxPGoDVc8MHlcOHiPuqKGQJC3z_JDkLk37Ypyeaa8HOdjZbAxPQlNEEs5DCOVwHhcvu5p2GMcEzH27O0JxUpTjbPZpgD_j4oLbbAu--vKKU3yCtYb2hVIXHES467aDZOZmf9cNur3PKwla_3-tFzVar22p3aKfbC-JmGrboiaARE-oMT0MEQc4WxLDAgqUzOuFnQTMImmGz3eq22x2I-Ciind5pL6DdpN_tJo12k2WUC78-NnFSnhmV4JFXwU1cxtTmJjgH6i3GzuzhixNa6bksz-502D8xcs-M3v8GXAjQhg">